Acne is a skin disease with usual onset at adolescence. It is characterized by the overproduction of sebum. One principle in treating acne has been to reduce the secretion of sebum. At the time of puberty, the sebaceous glands responding to hormonal influences increase the production of sebum excessively. Prior to the present invention, sebum secretion could only be suppressed by estrogen administration which is satisfactory for the treatment of females, but the side effects contraindicate the use of systemic estrogen in males. Labeled studies indicate that sebaceous cells form sebum from glucose. Glycogen is first synthesized and is then converted to grease and extruded into the duct as sebum.
An understanding of the roll of glucose in the synthesis of sebum is important. Factors governing glucose entry into the sebaceous cell are similar to those found in other cells where insulin plays a prominent role. The utilization of glucose by the skin of diabetics is diminished, but is enhanced by insulin in both normals and diabetics. The pathways to the synthesis of fatty acid are enhanced by insulin. (Can.J.Biochem. 44:801 1966). The stimulating effect of insulin on acne vulgaris has been demonstrated, (Zeit of Haut & Geschects Krank. 41:429 1966) and this investigation proved that lipids were synthesized by the skin under the influence of insulin. Wheatly presented a simple method for testing the formation of lipids in thin tissue slices. His data indicated that C-14 labeled glucose was the best precursor for the synthesis of cutaneous lipids. (J.Clin. Invest. Derm. 54:288 1970). It has also been found that drugs that interfere with sterol synthesis do not influence sebum formation. (Brit. J. Derm. 81:280 1969).
The normal sebaceous gland contains immature cells at the periphery of the sebaceous acini. These cells contain large nuclei which are usually larger than the cytoplasm. As the peripheral cells mature, large quantities of glycogen accumulate in the cytoplasm. This accumulation of glycogen results from the entrance of glucose into the cell and its conversion to glycogen. This anabolism appears to be stimulated by androgens. As cells undergo sebaceous transformation glycogen decreases concomitantly with the increase of lipid globules. (J.Invest.Dermatol. 17:147 1951; Anat. Rec. 114:231 1952). The concentration of glycogen in the cell is inversely related to the lipid concentration since it is decreased by the conversion of glycogen to lipid. As the concentration of lipid increases, the entire cell becomes converted to a mass of lipid. The entire lipid rich cell is destroyed and extruded into the duct of the gland. New cells at the periphery grow and replace the extruded cell.
Phloridzin is a glucoside which is a natural plant hormone present in apple root bark (Merk Index 1983 10:7211) and the seeds of young apple fruit (Nature 158:663 1946). The aglucone portion of phloridzin is a phenolic compound called phloretin. (Merk Index 10:7210 1983). Phloretin is insoluble in water and soluble in acetone and alcohols and sparingly soluble in the fat solvents benzene and chloroform, but phlorizin is soluble in hot water and alcohol, but insoluble in chloroform and benzene. Both phloridzin and phloretin are known generally to prevent the entrance of glucose into cells by blocking the glucose transfer sites on the cell membrane (Physiol. Rev. 25:255 1945; Harvey Lect. 56:63 1961). These compounds therefore prevent glycogen formation in cells and lead to glycogen depletion. They are relatively non-toxic and have been systematically administered to humans and animals. (Physiol.Rev. 7:385 1927) (Physiol.Rev. 25:255 1945; Am.J.Physiol. 219:1080 1970). Animals and humans respond to systemic administration with glucosuria since these drugs prevent tubular reabsorbtion of glucose from the glomerular filtrate. (Smith, H.S. The Kidney, Oxfor Univ. Press 1951, p. 97). Although phloridzin and phloretin have been extensively studied, they have remained medical curiosities with no previously known medicinal use.